Find the effective resistance of the network of resistors between points A and F as shown in the figure.

$\displaystyle R_{B C D}=2+4=6 \Omega$ $\displaystyle R_{B D}=\frac{3 \times 6}{6+3}=2 \Omega$ $\displaystyle R_{B D E}=2+8=10 \Omega$ $\displaystyle R_{B E}=\frac{40 \times 10}{40+10}=8 \Omega$ $\displaystyle R_{A F}=7+8+5=20 \Omega$